Apparatus for separating granular materials



AU8- 11, 1959 K. F. 'rRoMP APPARATUS FoR SEPARATING GRANULAR MATERIALS HAVING DIFFERENT sFEcIFIc GRAvIIIEs BY MEANS oF A LIQUID 3 Sheets-Sheet l Filed Sept. 23, 1957 FIC-).I

Augfll, 1959 2,899,058-

K. F. TROMP APPARATUS FOR SEPARATING GRANULAR MATERIALS HAVING DIFFERENT SPECIFIC GRAVITIES BY MEANS OF A LIQUID Filed Sept. 23, 1957 5 Sheets-Sheet 2 l Aug. 1l, 1959 K.

APPARATUS FOR SEPARATING GRANULAR MATERIALS HAVING DIFFERENT SPECIFIC GRAVITIES BY MEANS OF A LIQUID Filed Sept. '25, 1957 3 Sheets-Sheet 3 F. TRoMP i 1 2,899,058

United States Patent O APPARATUS FOR SEPARATING. GRANULAR MA- HAVlNG DIFFERENT SPECIFIC GRAV- rrrns BY MEANS or A LrQUm Claims priority, application Great Britain November 5, 1956 Claims. (Cl, lOl-4172.5)

This. invention relates toI aparatus for separating granular materialsv having `different specific gravities by means of a liquid.

It is well known in the` art that the progress of this separation is ideal if the liquid has a very low viscosity and is perfectly stagnant. In practice, however, stagnancy of the liquidis impossible to ensure, sincey the productsmust be discharged. continuously, which necessarily resultsin the creation of eddies in thev bath.

It is also known that ideal conditions for a static separation are best approached if horizontal currents are: created in the bath, provided always that the viscosity of' the liquid. is kept at a lowival-ue.

However, if a suspension of comminuted solids in. water` is used as the medium, wherein the separation is. to be carried out, and provided that no vertical currents are created therein, the specific gravity of the liquid Wilt not remain uniform throughout the entire depth of the bath, but will increase from the surface downward, theincrease being the ymore pronounced as the viscosity is; lower.

This phenomenon per se has proved not to bea serious; drawback, provided always that, in accordance with a known process, the middlings remaining suspended in the liquid are swept out of the separating space by means. of horizontal current and removed from the bath by suitable conveyance.

The realisation of said known process, wherein the conveyance is not allowed to create vertical currents in. the separating space, requires special constructions with. a View, inter alia, to minimizingl abrasion caused fby the: solids in the suspension. The sinks are discharged by a. rotary, bladed drum, whose front portion is provided with 1an impervious shell and whose rear portion is open, themiddlings being discharged by hydraulic means. How-- ever, hydraulic means for discharging the middlings aresuitable only if the grains of the material to be treated'. are relatively small.

The primary object of my present invention is an improved construction of the washing tank comprising a. rotary, bladed drum, so, that thisdru'm is capable to dis-l charge not only the sinks, 4but also the middlings.

In this connection it may be remarked'that it has al ready been suggested to remove both the sinks andthe middlings from the bath by means of a rotary, bladed drum., Ibut in that case the drum is associated with a. classifier or stream washer, i. e. with apparatus of a type that is radically different from the one to which my present invention relates.

lnorder that my invention may be readily understood, I shall now proceed to describe the same with referenceto theannexed drawing, wherein:

Fig. l is a vertical, longitudinal sectional view of one embodiment of my invention,

Fig. 2 is a sectional plan view along the line II-II in Fig. l,

Fig. 3 is a cross sectional view along the line III-lil inFig.. 1,

k 2,899,058 'rfatenaidA Aug. 11, 1959 Fig. 4 is a cross sectionalA view along the line IV-IV in Fig. 1', and

Fig. 5 is a diagram illustrating the manner in which the suspension removed from the apparatus is recycled.

The apparatus illsutrated in the drawing comprises a cylindrical trough 1, wherein two stationary, suitably spaced, longitudinal wallsv 2a, 2b are provided. In accordance with the drawing, these walls, which define the separation chamber, are vertical and have converging rear portions, but it is to be understood that they may also be parallel throughout, and/ or assume inclined positions. Both the top and the bottom edges of said walls are 'suitably spaced fro mthe cylindrical wall of the trough.

Mounted within the trough I is a bladed drum 7 rotatable in coaxial relation withy the trough and comprising both at its front and at its rear end a lantern wheel 8 whose studs are designated by 3, said Wheels being supported by rollers 4 and interconnected by a plurality of perforated blades 5. Gear wheels 6 meshing with the lantern wheels 8 are driven by suitable means not shown.

The front portion of the cylindrical portion of the bladed drum 7 prevents sinks engaged lby the rotating blades 5 from scraping andV scratching the wall of trough 1. Should this shell be completely impervious, granular materia-l reaching the gap between the shell and the cylindrical wallof the trough would be apt to get jammed therein, so as to accumulate therein, With a view to avoiding this accumulation, the shell 7 isprovided with a plurality of axial, circumferentially distributed and axially staggered slots 9, the trailing edge of each of which is provided with a narrow scraping blade 1t), which is inclined 'in forward direction and adapted to sweep the inner face of the trough.

During lrotation of the drum in the direction indicated by the arrow A in Figs. 3 and 4, said Scrapers carry the sludge that may have got intothe aforesaid gap upwards, so that, near the top of the dmm the sludge slides oifthe Scrapers and falls through ths slots 9 into the pockets between the blades 5.

Secured to the rear edge ofthe shell 7 is an inwardly projecting ring 11.

The walls 2a and 2b project from the front wall 17 of the trough 1 and enclose inlet conduits 12a, 13a, 14a and 15a, which are fed with suspension supplied by transverse pipes 12, 13, 14 and 15, respectively. These pipes are perforated to distribute the suspension supplied thereby uniformly over the full widths of the inlet con duits.

An inclined shoot 16. is provided for introducing the material to be treated, such as run-of-mine coal, to the drum 7, which, in operation, is partly lled with suspension, the surface thereof being indicated by S. The mouth of shoot 16 is substantially ush with said surface.

The walls 2a, 2b also projectl from the rear walll 18 of the trough 1 where they form part of a shoot/19V for discharging the floats, which, in their movement towards said shoot, are guided by an upwardly inclined plate 20, which interconnects the walls 2a and 2 b and forms a Weir. 21.

Mounted within theupper part of the bladed drum 7 and slightly spaced from, the blades 5 thereofis` a, stationary, cylindrically curved plate 22 coaxial withthe drum. Onev axial edge of said plate is located,A close to the horizontal plane passing throughf the axisy of the drum, the other edge being secured to two hoppers 2,3 and 24.

The minor` rear portion of the bladed drum is open, i.e. devoid of a shell. In. the. region of said open drum section the. top segment. of the plateA 22. has, an opening ice covered by a `sieve 22a, and secured to the axial edges of said opening is a third hopper 25.

The three hoppers 23, 24 and 25 project from the rear wall of the trough 1 at different levels thereof.

Slightly spaced from the inner edge of the ring 11 are vertical, transverse partitions 26 and 27 extending upwards to a level above the surface S of the bath. These partitions are interconnected by the plate 20 and have for their purpose to isolate the suspension in the open portion of the bladed drum from the suspension in the other portion of the wheel outside the separating chamber.

Mounted intermediate the partition 27 and the rear wall 18 of the trough `is a relatively small paddle wheel 28 adapted to rotate about an axis parallel with that of the drum 7 and in the same direction as said drum, owing to the wheel 28 being engaged by the lantern wheel 8.

As shown in Fig. 4, the wall 2b has an opening 2b bounded by the rear wall 18 of the trough, the partition 27 and the plate 20.

The bottom of the trough 1 below the open portion of the drum is perforated as yat 30, `a discharge hopper 29 being mounted below said perforated bottom part.

Finally, the trough 1 has another discharge hopper 31 opening into the region of the open portion of the drum somewhat below the liquid -surface S, where the drum moves in upward direction. A sieve 32 covers said openin-g, so that it is shaved by the blades of the rotating drum.

The apparatus described so far operates as follows, provided that the bladed drum 7 is rotated in counterclockwise direction as seen in Figs. 3 and 4 and that suspension is supplied to the pipes 12, 13, 14 and 15, which suspension is discharged, at controlled rates, partly by the weir 21, partly by the hoppers 29 and 31.

Owing to the absence of vertical currents in the bath and to the fact that the suspension supplied by the pipes 12, 13, 14 and 15 is introduced horizontally into the separating chamber between the walls 2a, 2b and through the full width thereof, the density of the suspension in the bath will increase from the surface to the bottom, so that the suspension discharged by the weir 21 will have a density lower than that of the suspension discharged by the hopper 31, and that the latter suspension will have a density below that of the suspension discharged by the hopper 29.

If, for instance, run-of-mine coal is supplied, by the shoot 16, to the bath, the pure coal will oat on the suspension in the separating chamber and be driven, by the current of suspension `supplied by pipe 12, towards the weir 21.

The products of relatively high specific gravity will sink and be received by the pockets between the blades 5 of the drum 7, and are carried by said blades across the cylindrical plate 22 towards and 4into the hopper 23.

The middlings, having a specific gravity intermediate those of the products discharged by the weir 21 and the hopper 23, respectively, remain suspended in the bath and are swept towards the rear end of the washing tank under the thrust of the suspension supplied by the pipes 13, 14 and 15.

Owing to the high density suspension being discharged by the hopper 29, the high gravity middlings fall onto the sieve 30 and are collected by the upward moving blades of the drum 7.

The medium density suspension is discharged by the hopper 31, and the low gravity middlings suspended therein are drawn into contact with the sieve 32 and thus also collected by the blades 5 of the drum.

In order that the suspension flowing directly below the inclined plate 20 may discharge said low gravity middlings, it must follow a sharply bent path, owing whereto part of said middlings would be liable to accumulate locally, whereby the discharge of said products would be impaired. By the provision of the paddle wheel 28 this diiculty is efficiently met, since this wheel positively 4 draws the current of suspension in the desired direction and through the full widths thereof.

The high and the low density middlings are discharged, across the curved plate 22, by the hopper 24.

In certain cases it may be desirable for at least part of the finer fraction of the middlings to be added to the pure coal. It is with a view thereto that the curved plate 22 is suitably perforated vertically above the hopper 25. This has a practical advantage. It is well known that the ash content of the coarser grains of run-of-mine coal floating on the liquid and having a specific gravity of sayl.5, i.e. the grains having a size of say between 6 and l inch, is higher than that of the liner grains, having a size of say between 1 and 1A inch. However, as far as the ash content is concerned, the coal trade makes more exacting demands on coarse coal than on finer coal, and it is for this reason that it is suggested for the apparatus in accordance with the invention to be provided with means whereby the fine middlings can be added to the washed coal, if so desired.

Although the drawing illustrates an apparatus wherein the pure coal is discharged under the thrust of a substantially horizontal surface current in the bath, it will be understood that it lies within the ambit of the invention to provide the washing tank with additional mechanical means such as a drag conveyor, paddles or the like for supporting said hydraulic discharge.

As stated above, the suspension discharged together with the sinks, the middlings and the coal and by the hoppers 29, 31 should be returned to the washing tank. Should this suspension be recycled directly to the pipes 12, 13, 14 and 15, the differences between the specific gravities of the floats and the middlings, on the one side, and of the middlings and the sinks, on the other side, will be relatively small. This direct recycling of the suspension will be practical, for instance, if it is desired for the middlings to have a low ash content, or when the run-of-mine coal is to be separated into only two fractions, in which latter case the hoppers 23 and 24 could be combined. In these cases, the paddle wheel 28 and/ or the suspension outlet 31 could be dispensed with if the relative amount of middlings is small enough.

If, however, the run-of-mine coal is to be separated into three fractions with greater differences between their specific gravities, it is suggested to recycle the suspension in the manner diagrammatically shown in Fig. 5. As illustrated, the heavier suspension discharged as at 29 is returned to the washing tank via a control valve 42 and a sump 39, which is connected, through a valve 40, with the suction side of a pump 41 whose delivery pipe is connected to the feed pipe 15, which, as shown in Fig. l, opens into the trough near the bottom thereof. The remaining suspension is discharged, via a control valve 43, into a sump 36 connected to the suction pipe of a pump 37, whose delivery pipe distributes part of this suspension over the feed pipes 12, 13 and 14 (if desired also over pipe 15, through a valve 38), another part thereof being supplied to the hoppers 23 and 24 to wash the sinks and the middlings over to the relative sieves.

To increase the differences between the specific gravities of the fractions, it is recommended for the surface area of sump 39 to be relatively large and for the suspension therein to overflow into sump 36.

Thev differences between the specific gravities of the fractions can still further be increased by thickening the suspensions to be fed to the pipes 13, 14 and 15.

What I claim is:

l. Apparatus for separating granular material having different specific gravities by means of a suspension, comprising, in addition to a cylindrical trough, a bladed drum extending through practically the entire length of the trough and mounted fo-r coaxial rotation therein so as to just clear the cylindrical wall thereof, the front portion of said drum preferably being provided with a substantially impervious shell and the rear portion thereof being open',

the trough being provided, in addition to two suitably spaced longitudinal walls secured to its front and rear Walls and defining a separating chamber, with means for supplying the material to be separated and means for supplying suspension to said chamber at the front end thereof, and with a shoot in the rear wall of the trough for discharging the surface layer of the suspension together with the floating fraction of the said material, wherein the bottom of the trough is provided, close to the rear wall of the trough, with an outlet opening covered by a sieve just cleared by the blades of the rotary drum.

2. Apparatus in accordance with claim 1, wherein that portion of the drum which is comprised substantially between the vertical planes passing through the front and the lrear edges of the said sieve is separated from the front portion thereof by an inwardly extending ring member.

3. Apparatus in accordance with claim 2, wherein stationary partitions are provided intermediate said ring member and the said longitudinal walls, said partitions just clearing the inner edge of the ring member and extending upwards to a level above the surface of the suspension in the trough.

4. Apparatus in accordance with claim 3, wherein a paddle Wheel is mounted, so as to be rotatable in the same direction as the drum, within the space intermediate the rear wall of the trough and the partition on that side of the trough, where the drum during its rotation moves upwards, so that only the lower paddles of said wheel are immersed in the bath.

5. Apparatus in accordance with claim 3, wherein the trough is provided with an outlet opening close to the rear wall thereof and somewhat below the surface of the bath, said opening being located on that side of the trough Where the drum during its rotation moves upwards, and being covered by a sieve member just cleared by the blades of said drum.

References Cited in the tile of this patent UNITED STATES PATENTS 2,521,152 Davis Sept. 5, 1950 FOREIGN PATENTS 554,285 Great Britain June 28, 1943 495,540 Canada Aug. 25, 1953 

